1. Technical Field of the Invention
This invention relates to radio telecommunication systems and, more particularly, to a system and method of interfacing digital mobile radio voice and fax protocols with Internet Protocols.
2. Description of Related Art
Recently, Internet (Internet Protocol (IP)-based) telephone products and services have been introduced that promise enhanced speech quality and connectivity to other Internet subscribers and to regular (non-IP) telephone subscribers. With increases in Internet bandwidth and the deployment of enhanced IP-based, real-time protocols (RTP) and reservation protocols (RSVP), the Internet is poised to eventually offer the type of speech quality that standard land-line subscribers have come to expect. These developments are not just limited to the public internet, but apply to private intranets and Local Area Networks (LANs) as well.
The Internet already offers broadcast and multicast capabilities (through MBONE routers) that have the potential to emulate conference call services. Other computer telephony features using the Internet are now finding their way into commercially available software applications.
Existing radio telecommunication systems such as the Global System for Mobile Communications (GSM, Time Division Multiple Access (TDMA) systems such as the Digital Advanced Mobile Phone System (D-AMPS) (IS-136), Code Division Multiple Access (CDMA) (IS-95) systems, and Personal Communication Services (PCS) systems all utilize digital speech codecs for the transmission of speech information, and have all specified support for a digital asynchronous circuit-mode data service utilizing an Interworking Function (IWF). The standards for these systems are hereby incorporated by reference herein. The role of the IWF is to provide a translation function between the specialized data protocols used by the radio telecommunication systems and the standard land-line data protocols. More specifically, the IWF provides translation functions between the digital radio link protocols (RLP) and land-line analog modems, Integrated Services Digital Network (ISDN) terminals, terminal adapters, and packet data networks. Functions performed in the IWF include rate adaptation between the transmission rate over the air interface and the transmission rate over the land lines. Thus, the IWF performs flow control, error control, sequence control, data buffering, encryption, compression, etc.
The existing IWF, however, does not perform interworking functions between mobile-specific voice encoding protocols on the mobile radio side of a connection and Voice-over-Internet Protocol (Voice-over-IP) encoding protocols (sometimes referred to as Voice-on-Net or VON) on the Internet side of the connection. Likewise, the existing IWF does not perform interworking functions between mobile-specific fax encoding protocols on the mobile radio side of a connection and Fax-on-Internet Protocol (Fax-on-IP) encoding protocols on the Internet side of the connection.
Although there are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that disclosed herein, several references discuss subject matter that bears some relation to matters discussed herein. European Patent Application EPO 740 445 A2 discloses a method and system for establishing voice communications using a computer network. However, this reference discusses communications with the Internet only from landline telephone networks. There is no teaching or suggestion of an enhanced IWF for interfacing mobile terminals directly with the Internet.
PCT Patent Application WO 96120553 discloses a unified messaging and communication system which utilizes the global Internet to link multiple local landline telephone networks. This reference discusses communications with the Internet only from landline telephone networks. There is no teaching or suggestion of an enhanced IWF for interfacing mobile terminals directly with the Internet.
PCT Patent Application WO 96/29808 discloses a system and method of simultaneously transmitting voice and data on shared voice telephone lines. The system permits a single computer or a plurality of computers to be connected to a central computer network using existing telephone wires which continue to provide the normal voice access to the Public Switched Telephone Network (PSTN). This reference discusses communications with the Internet only from landline telephone networks. There is no teaching or suggestion of an enhanced IWF for interfacing mobile terminals directly with the Internet.
PCT Patent Application WO 96/34341 discloses a message storage and delivery system which is connected to a plurality of direct inward dialing (DID) phone lines and receives facsimile messages, voice messages, and data messages. The messages are stored in memory and converted to hyper-text mark-up language (HTML) for transmission over the Internet. Users can access the message storage and delivery system either though the telephone network or the Internet. However, this reference discusses communications with the Internet only from landline telephone networks. There is no teaching or suggestion of an enhanced IWF for interfacing mobile terminals directly with the Internet.
Review of each of the foregoing references reveals no disclosure or suggestion of a system or method such as that described and claimed herein.
In order to overcome the disadvantage of existing solutions, it would be advantageous to have an enhanced IWF (E-IWF) for performing interworking functions between mobile-specific voice encoding protocols and Voice-over-IP encoding protocols as well as performing interworking functions between mobile-specific fax encoding protocols and Fax-on-IP encoding protocols. Such an E-IWF would provide a means for a mobile station to interface voice and fax with the Internet, directly or indirectly through an E-IWF that may be associated with a mobile switching center (MSC). The present invention provides such an enhanced IWF.
In one aspect, the present invention is an enhanced IWF that supports direct digital interwork between a radio telecommunications network and standard IP networks comprising routers via, for example, an Ethernet (CSMA/CD IEEE 802.3) interface. The present invention supports speech transcoding and data interworking within a general purpose IWF, and provides specific translation from the specialized air-interface encoding methods (e.g. Vector Sum Excitation Linear Predictive (VSELP) vocoders, Adaptive Codebook Excitation Linear Predictive (ACELP) vocoders such as an Alternate Full Rate (AFR) codec standardized in IS-641, GSM Enhanced Full Rate (GSM-EFR), etc.) directly to Voice-over-IP protocols. In different embodiments, this is accomplished with or without an intermediate pulse code modulation (PCM) or analog conversion.
In another aspect, the present invention is a method of supporting direct digital interwork between a radio telecommunications network and standard Internet Protocol (IP) routers. The method comprises the steps of performing speech transcoding and data interworking with a general purpose interworking function, and translating between specialized air-interface encoding methods and Voice-over-IP protocols with a specific translation interworking function.
In yet another aspect, the present invention is a method of interworking between cellular voice protocols in a time division multiple access (TDMA) cellular telecommunications network, and Internet protocols being utilized by an Internet End-System (ES). The method begins by encoding a voice signal from a mobile station in one of the cellular voice protocols, creating a voice frame from the encoded voice signal, interleaving the voice frame into one or more TDMA bursts, and transmitting the TDMA bursts over a radio link to a base station. The voice frame is multiplexed in the base station and transmitted to the E-IWF. This is followed by transcoding the voice frame in a first codec into an isochronous stream of digitized voice samples, transcoding the stream of digitized voice samples in a second codec into a Voice-over-IP service data unit (SDU), and framing the SDU with a transport layer protocol. The step of transcoding the voice frame in a first codec into an isochronous stream of digitized voice samples such as PCM or adaptive differential pulse code modulation (ADPCM). The framed SDU is then carried by a data link layer network interface and physical layer transmission media. The method then interfaces with an Internet Service Provider (ISP).
In yet another aspect, the present invention is a method of interworking between cellular fax protocols and Internet protocols, the cellular fax protocols being utilized by a mobile station in a time division multiple access (TDMA) cellular telecommunications network to transmit an image to a far-end fax machine via the Internet, and the Internet protocols being utilized by a fax gateway. The method begins by originating a mobile fax call, setting up a Radio Link Protocol (RLP) for communicating between the mobile station and the cellular telecommunications network, and scanning, encoding, and compressing the image into a fax data stream. This is followed by sending a sequence of digitized call establishment signals between an enhanced interworking function (E-IWF) in the cellular telecommunications network and the far-end fax machine, formatting the fax data stream into User Datagram Protocol (UDP) frames and segmenting the frames into Internet Protocol (IP) datagrams, and transmitting the UDP/IP datagrams over the Internet to the fax gateway. The method then performs the steps of converting, in the fax gateway, the UDP/IP datagrams into fax modem voiceband information, sending the fax modem voiceband information to the far-end fax machine, and recreating the image in the far-end fax machine.